This invention relates to an intake port shape of internal combustion engine, and particularly to an intake port shape of internal combustion engine which produces a swirl by using a direct port.
In the internal combustion engine of such a type, various technologies and studies have been made to improve an intensity of swirl flow by controlling a direction of intake flow in an intake port or at an outlet of the intake port, and there are a shroud valve method, a masked plate method and a stepped port method etc.
The shroud valve method has a structure in which a shroud for direction control is formed on an intake valve, the masked plate method has a structure in which an annular masked plate provided with an inward extending surface is installed between a valve seal and a seat fitting annular stepped surface as showed in Published Patent Application (KOKAI) No. 63-131824, and the stepped port method has a structure in which an inward extending inclined wall is formed on an inner peripheral wall of intake port as showed in Published Patent Application (KOKAI) No. 8-189366.
(Technical Problem to be Solved by the Invention)
In the shroud valve method, it is required to equip a locking mechanism to the intake valve in order to secure a position of the shroud. Therefore, a structure becomes complicated to cause a cost increase, and one-sided wear is apt to occur on the intake valve due to locking and thermal deformation of the valve, so that this method includes a problem of durability. In addition, a flow coefficient is also worsened because a flow sectional area is practically reduced by the shroud.
In the masked plate method, a flow sectional area of the intake port is abruptly reduced so that the flow coefficient is worsened. Also, its plate member will cause a problem of durability.
In the stepped port method showed in Published Patent Application (KOKAI) No. 8-189366, a crescent extending portion is formed on a seat fitting stepped surface. In such a shape of flow restriction type, the flow sectional area of intake is remarkably reduced to cause a worsening of flow coefficient due to an excessive increase in a extending amount of arc-shaped inner peripheral edge of the extending portion in order to efficiently restrict a valve stem collision flow which is a maximum counter swirl flow.
(Object of the Invention)
An object of the present invention is to restrict a part of intake flow which is apt to flow in a direction opposite to a swirl flow after colliding with a valve stem, and to produce an intense swirl flow while controlling a worsening of flow coefficient. To prevent the one-sided wear and to improve the durability are also objects of the present invention.
(Solution for the Problem)
An invention as claimed in Claim 1 of the present invention is characterized by that, in an intake port shape of internal combustion engine wherein an annular stepped surface 14 for supporting a valve seat is formed on an intake port outlet portion of a cylinder head 1, and an end face of a valve seat 4 is made contact with the annular stepped surface 14 to support it,
a shape of an inner peripheral edge of the annular stepped surface 14 includes a shape of an inner peripheral edge 4a of the valve seat 4 as its base circle, and has an extending portion 15 projecting toward a valve stem 11 side at a radial inlet side portion of an intake port, and
the extending portion 15 is formed into a mountain-like shape which widens from a top portion 15a projecting toward the valve stem side to both peripheral sides with moderate inclinations, and finally connects to the base circle at both foot ends, and
a ridge-like back wall 16 is formed at a side opposite to a valve seat side of the extending portion 15, the back wall decreasing its projecting height toward an upstream side along an intake port 2 and connecting smoothly to an inner peripheral wall surface of the intake port 2.
An invention as claimed in Claim 2 of the present invention is characterized by that, in an intake port shape of internal combustion engine wherein an annular stepped surface 14 for supporting a valve seat is formed on an intake port outlet portion of a cylinder head 1, and an end face of a valve seat 4 is made contact with the annular stepped surface 14 to support it,
a shape of an inner peripheral edge of the annular stepped surface 14 includes a shape of an inner peripheral edge 4a of the valve seat 4 as its base circle, and has a extending portion 15 projecting toward a valve stem 11 side at a radial inlet side portion of an intake port,
the extending portion 15 is formed into a trapezoidal shape which has a flat top portion 15a projecting toward the valve stem side, widens from the flat top portion 15a to both peripheral sides with moderate inclinations, and finally connects to the base circle at both foot ends, and
a ridge-like back wall 16 is formed at a side opposite to a valve seat side of the extending portion 15, the back wall decreasing its projecting height toward an upstream side along an intake port 2 and connecting smoothly to an inner peripheral wall surface of the intake port 2.
An invention as claimed in Claim 3 of the present invention is characterized by that, in an intake port shape of internal combustion engine wherein an annular stepped surface 14 for supporting a valve seat is formed on an intake port outlet portion of a cylinder head 1, and an end face of a valve seat 4 is made contact with the annular stepped surface 14 to support it,
a shape of an inner peripheral edge of the annular stepped surface 14 includes a shape of an inner peripheral edge 4a of the valve seat 4 as its base circle, and has a extending portion 15 projecting toward a valve stem 11 side at a radial inlet side portion of an intake port,
the extending portion 15 is formed into an arc-like shape with respect to the base circle, and
a back wall 16 is formed at a side opposite to a valve seat side of the extending portion 15, the back wall decreasing its projecting height toward an upstream side along an intake port 2 and connecting smoothly to an inner peripheral wall surface of the intake port 2.
An invention as claimed in Claim 4 of the present invention is characterized by that, in an intake port shape of internal combustion engine as claimed in claim 2 or 3, a partially circular concave portion is formed on the top portion 15a with a specified distance kept from the valve stem 11.
An invention as claimed in Claim 5 of the present invention is characterized by that, in an intake port shape of internal combustion engine as claimed in claim 2 or 3, a mountain-like top portion projecting toward the valve stem side is formed at the trapezoidal or arc-like extending portion.
An invention as claimed in Claim 6 of the present invention is characterized by that, in the intake port shape of internal combustion engine as claimed in any one of claim 1 to claim 5, a rounded valve seat is installed for serving as the valve seat.
(Effect Superior to Prior Art)
(1) Conventionally, a part of intake flow has been made collide against the valve stem or valve head to produce counter swirl flow. In the present invention, this part of intake flow is made uniform and divided to both sides of the valve stem by the back wall 16 to avoid collision against the valve stem in a flow course from midway of the intake port 2 to the extending portion 15 of the valve seat fitting annular stepped portion 14, and the intake flow in a direction of counter swirl is restricted by reducing an upstream side space in a radial direction of the valve stem 11 through means of the top portion 15a extending to the valve stem side. Thus, the swirl flow can be intensified.
(2) Since it is not required to lock the intake valve as in case of the conventional shroud method, the one-sided wear of the intake valve due to thermal deformation etc. can be prevented and the durability of valve can be maintained. Further, there is no possibility of wrong assembling of the intake valve and deviation of stem axis.
(3) The flow sectional area is changed by forming the back wall 16 followed by the extending portion 15 at the upstream side of the annular stepped surface 14. Consequently, the intake flow is made uniform from the upstream side within the intake port, so that a pressure loss can be reduced, as compared with the conventional shroud valve method and the mask plate method.
(4) In the invention as claimed in Claim 1, the extending portion 15 is formed into the mountain-like shape which extends from the top portion 15a projecting toward the valve stem side, to both peripheral sides with moderate inclinations, so that a percentage of a masked area in the vicinity of the valve stem 11 becomes large. Therefore, while effectively restricting the intake flow which is apt to flow in the direction opposite to the counter swirl flow after colliding against the valve stem 11, a decrease in the flow sectional area can be minimized and a lowering of the flow coefficient can be prevented.
(5) In the invention as claimed in Claim 2 or 3, since at least the top portion of the extending portion is made flat, a cast molding becomes easy.
(6) In the invention as claimed in Claim 4 or 5, since the extending portion has the shape of combination of the mountain-like shape with the arc-like or trapezoidal shape, the sectional area of extending portion can be increased and the swirl flow can be intensified further while controlling the lowering of the flow coefficient, as compared with the mountain-like shape alone, the trapezoidal shape alone, or the arc-like alone.
(7) When a rounded valve seat 24 is installed for serving as the valve seat as described in the invention as claimed in Claim 6, a peeling-off of intake flow is reduced at a border between the bottom of a seat surface 23 and a lower rounded surface 21. This effect is remarkable at a part where no extending portions existing, and a counter swirl flow is relatively reduced. Thereby, the swirl flow is further intensified.